Until now, to permit movement of a welding tong necessary for the production process, it was usual to suspend said welding tong and its accessories from rolling rails, which are fixed to the framework of the assembly plants by removable sub-frames. Such an installation requires connection to the ground of the welding tong, by means of a connection foot, and an associated detection system.
The assembly of the sub-frame bearing the rolling rails must be constructed as a function of the assembly line in question, such that dismantling is necessary for installing a new line with its specific rail system. These operations are long and costly, the structure constituted by the subframe and the rolling rails being itself difficult to design, produce and assemble.
A modification of the assembly line is extremely difficult and costly.
Another drawback of the known system which has been described resides in the great difficulty of reusing in a new line the material thus installed, because of the specific definition of the suspended working station.
Repairs and exchanges of components are also difficult because of the suspension of a working unit which must accordingly be as integrated as possible.
There are also known several devices for suspension of manually controlled tools.
Thus, from JP-A-59037006, there is known a work station for a piercing tool in which said tool is carried by a suspended mast with a bracket along which said mast is displaceable. This bracket is moreover connected to one end of a support resting on the ground and about which it is movably driveable.
Such a device requires in the first instance a counterweight on the mast itself so as to counterbalance the weight of the piercing tool and then requires perfect securement of the central support carrying the bracket. Thus, when said mast is brought to the end of the bracket, this can generate a twisting force on the central support which has to be countered by good securement. Once the piercing tool has been brought adjacent the object to be pierced, as recognized by an electromagnetic magnet, this piercing tool is correctly positioned. This positioning takes place manually by manipulation of handles suitable to displace said tool forwardly and rearwardly, up and down and from left to right.
The tool in question being a piercing tool, it is necessary to obtain precise positioning of said tool. However, in the case of the welding tong, it is on the contrary important to provide complete freedom of manipulation in movement of said tool by the user and such a device therefore cannot be used in a welding station.
There is also known, from U.S. Pat. No. 4,969,625, a device for manually controlled tools, in particularly a fastening device in which there is provided a drive means for moving said tool back and forth, laterally, forwardly and rearwardly and vertically, as well as for driving it in rotation. These means are provided on a longitudinal axle whose one end is secured on a vertical mast having a positioning plate and whose other end carries the tool. The device also comprises torsion reaction means and means for securing the mast in a working plane. However, this device has a particularly complicated and rigid structure which also does not give complete freedom of manipulation and movement for the user.
The device described in U.S. Pat. No. 3,608,578 also relates to a device for manual tools in which a mast is mounted on a workbench and comprises a support. This support comprises a transport mechanism which moves along the latter and which carries a balancing device having a cable to which is fixed the tool. To drive the tool in displacement to the desired working position, one pulls on the cable. This support is mounted pivotably about the mast and comprises at its other end a filter and a lubricator connected by a conduit to a source of compressed air.
This filter and this lubricator can also serve as counterweights for the balancing device of the tool. However, the positioning of these members prevents the latter from being too voluminous and moreover, during maintenance or repair operations, these members are not readily accessible.
In U.S. Pat. No. 5,367,924, there is disclosed an arm support for a screw-making machine. This arm support permits avoiding transmission of the force of rotation generated by the screw-maker to the hands and to the wrists of the operator. This arm support moves in particular along an axis transverse to the suspended chassis. However, such a device is limited in its freedom of manipulation and displacement by the operator.
In DE-A-19623265, published after the priority application of the present application, there is described a device for suspending a welding tong comprising a column fixed to the ground on which is mounted, pivoting about it, an arm. The welding tong is mounted articulatedly, is displaceable vertically and forward and rearwardly with the help of a balancing device. The tong is also mounted on rolling rails mounted parallel to each other and perpendicular to the arm itself, such that said tong moves from left to right.
The welding transformer is also mounted on the support sufficiently high that users may pass below it without striking it. Also, when the mast is driven in rotation about the column in the course of different operations, this drive can be difficult because of the weight of the welding transformer, whilst the drive for moving it from left to right is limited by the length of the rolling rails.
The present invention seeks to overcome the drawbacks of the known systems.